Bath Mixer Taps – Problem Solving
Bath mixer restrictions
There are several restrictions on fitting bath mixer taps. Make sure you understand them before buying, since they could affect what sort of tap you choose.
For all types of mixer tap, check whether the model you plan to buy mixes the hot and cold supplies in the body of the tap or keeps them separate until they leave the spout.
If the tap is the ‘mix in body’ type, but the hot and cold supplies are fed via a cold storage tank and hot water cylinder, you have no problems. However, if the cold supply comes direct from the mains, the Water Byelaws insist that you fit a double check valve assembly directly below the inlet to the tap to guard against stored hot water being siphoned back into the mains.
On taps which keep the flow separate, if the supply is from the mains, check that the diverter valve is spring-loaded to guard against back-siphonage of waste bath water through the hose. If not, you must fit a double check valve.
For shower mixer taps there are some practical considerations.
If the supply is via a cold storage tank and hot water cylinder, the water outlets from the tank should be sufficiently high above the shower head to give a reasonable amount of pressure (the ‘head’ as it is known in the trade). About lm (3ft) is the minimum acceptable, otherwise you could find the diverter valve keeps switching back to the bath-filling position.
Another point to consider is the number of other taps branched off the same supply pipes. Theoretically, turning several taps on at the same time could alter the shower pressure (creating a risk of scalding unless the mixer is thermostatically controlled). In practice the risk is usually minimal and is worth taking. But if you do experience pressure drop problems, the only solution is to run new supply pipes to the tap directly from the cold storage tank and from the hot water cylinder vent pipe, close to the cylinder.
If you’re fitting a conventional mixer and the pipes are the wrong way round (ie with cold on the left), you should be able to solve the problem by swapping the coloured indicators on (or in) the handles.
However, on thermostatic mixers you have to reverse the pipes so that the controls aren’t the wrong way round. The easiest way to do this is by fitting a pair of bendable connectors with tap connector fittings at one end and compression, soldered or push-fit joints on the other.
Shape the connectors to make the cross-over before you cut the supply pipes though, otherwise you are likely to find they don’t fit.